WO2018224092A1

WO2018224092A1 - Production of nanoparticulate compressed tablets (pellets) from synthetic or natural materials using a specially developed grinding and compressing method

Info

Publication number: WO2018224092A1
Application number: PCT/DE2018/100533
Authority: WO
Inventors: Carl-Dieter GARBE-SCHÖNBERG; Samuel MÜLLER; Simon NORDSTAD
Original assignee: Christian-Albrechts-Universität Zu Kiel
Priority date: 2017-06-08
Filing date: 2018-06-05
Publication date: 2018-12-13
Also published as: CA3066477C; AU2018279770A1; DE102017112691B4; CA3066477A1; US20200140341A1; AU2018279770B2; DE102017112691A1; EP3635362A1; US11656158B2

Abstract

The invention relates to a method for producing nanoparticulate compressed tablets/pellets from synthetic and/or natural materials. The invention also relates to compressed tablets/pellets produced using a method for producing nanoparticulate compressed tablets/pellets from synthetic and/or natural materials and to uses thereof.

Description

Production of nanoparticulate pressed tablets (pellets) from synthetic or natural materials according to a specially developed milling and pressing process

The invention relates to a compressed tablet / pellet production process of nanoparticulate pressed tablets / pellets of synthetic and / or natural materials, comprising the steps:

- Preparation of an analysis fine ground powder with particle size <75 μηι

and

- Pressing at least one aliquot thereof in a high pressure press into a tablet / pellets.

Furthermore, the invention relates to a pressed tablet or a pellet and uses thereof.

In addition to mobile X-ray scanners, micro-analytical methods for elemental concentration determinations directly on solids are becoming more and more universally applicable and are widely used, e.g. in research, materials quality assurance or mining exploration.

However, there are hardly any standards suitable material with sufficient homogeneity in order to calibrate the corresponding analysis methods and to be able to secure measurement results.

On the micrometer scale homogeneous natural materials, e.g. Crystals, are extremely rare or very difficult to produce. Homogeneous synthetic glasses are difficult and can not be produced by all substances. Powdered pressed tablets, also referred to as pellets in the past, were previously too coarse for microanalysis and mostly contained a binder.

From the prior art, a production process for corresponding pellets is known, which the publication "Nano-particulate pressed powder tablets for LA-ICP-MS" by D. Garbe-Schönberg and S. Muller published on April 16, 2014 in The Royal Society of Chemistry, J. Anal. At. Spectrom., 2014, 29, 990. The prior art from this publication is explicitly included in this reference.

In the following, the problems of the prior art are briefly listed, which are processed on this side and which are solved with the disclosure on the side, namely:

Problem of Analytical Chemistry:

To calibrate and validate microanalyses directly on solids

Standard reference materials (SRM) are required which should be as similar in their properties as possible to those of the unknown samples (matrix matching). These SRM must be so homogeneous at each point that microanalyses with eg 1 μηι to 100μηι spatial resolution always the same result within a given

Confidence range, and this also applies to trace and ultra trace elements, but it is extremely difficult, expensive and expensive to find so homogeneous materials in nature or to produce technically.

Use as SRM so far find natural or synthetic glasses, natural or synthetic minerals, metals or metal alloys, powder pressed tablets of natural or synthetic substances or mixtures of substances.

- Glass:

Many materials can not be melted and processed into a homogeneous glass. When melting, volatiles are lost from the original material. Glasses have different properties than e.g. crystalline materials. There are very few natural homogeneous glasses.

- Metals:

Diffusion within the metal creates heterogeneity during manufacture.

minerals:

Over larger areas (mm-cm scale) sufficiently homogeneous and in larger quantities required (> 300-500g) occurring natural minerals are very rare.

In the production / breeding of synthetic minerals heterogeneity arises and it is very difficult to produce crystals that have the necessary homogeneity over larger areas.

Pressed powder tablets:

Persistent pressed tablets made of powders have so far been produced only with the addition of binders.

The particle sizes in the range of 10-100 μηι of "normal" finely ground powder are far too coarse and thus unsuitable for microanalyses with spatial resolution of 1-100 μηι compacts of nanoparticles, which were prepared according to the bottom-up (SdT) principle , are extremely expensive, the material adaptation to natural materials with more complex

Composition (50+ elements) is hardly possible.

The object of the invention is to demonstrate new possibilities for producing homogeneous standards for a variety of materials.

Press tablets / pellets made of synthetic or natural materials are to be produced according to a newly developed grinding and pressing process. These tasks are solved with the corresponding feature combinations according to the main claim and according to the independent claims.

The compressed tablet / pellet manufacturing process of nanoparticulate pressed tablets / pellets of synthetic and / or natural materials comprises the steps:

- Preparation of an analysis fine ground powder with particle size <75 μηι

and

Pressing at least one aliquot thereof into a tablet / pellet in a high pressure press,

being between the aforementioned steps

- First, a wet grinding of finely ground pulverulent powder in one

Grinding arrangement, jet mill grinding arrangement and / or high energy ball mill grinding arrangement takes place to a regrind;

- In addition, a transfer and drying, thermal drying or freeze-drying of the ground material to a nanopowder occurs

and

- then rehomogenize the dried nanopowder,

in which

the at least one aliquot is selected for pressing from the dried and rehomogenized nanopowder,

- The pressing is done without the addition of a binder,

and

- A nanoparticulate powder with grain sizes D90 <1 μηι is formed.

Nanoparticles are produced using this top-down principle, which can be pressed to form stable tablets without further binders.

The very small particle sizes ensure excellent homogeneity down to the micrometer range.

Low porosity and excellent surface quality of the tablets allow their

Surveying with electron or ion beam measurement in high vacuum.

The nano-tablets also offer better properties for measurements with X-ray fluorescence (X-ray scanner) than previously used powder compacts. This will prove the

Tablets as a new universal material that can be studied with many different micro-analysis methods and therefore have great potential for being a certifiable standard reference material for both elemental and

Isotope composition. The this-world manufacturing process includes an ultra-fine grinding, also referred to as "top-down" principle, nanoparticles, followed by freeze-drying, and the pressing of the nanopowder, in particular with sapphire disks in a preferably programmable high-pressure press.

An optional and preferred reinforcement of the tablets externally (edge, back) with pressing aids, e.g. Cellulose, boric acid (sandwich) is possible and useful.

This method allows the production of stable pressed tablets of synthetic and / or natural materials, which are converted into nanoparticles, according to the top-down principle, which also makes very complex compositions

Materials become feasible.

In a particularly preferred embodiment variant, the nanoparticulate powder having particle sizes of 30-150 nm with D90 <1 μm is formed.

The extremely small particle size in this case allows a very good homogenization of substances / mixtures of substances (10-100 μηι scale).

Compared with the state of the art, for example from Garbe-Schönberg and Müller, 2014 (see introduction to the SdT) reproduced state is the this-sided process by continuous improvement of the state of the art today by two orders of magnitude better in the particle size and surface quality of the tablets.

Significant changes to the prior art exist in the type of mill used, the grinding protocol, and in a fundamental change in the pressing process in the

Tablet manufacturing.

The pressing of the aliquot is preferably carried out in a high-pressure press in the working range of 2 to 80 1, 3 to 40 or especially 5 to 20 1.

Furthermore, pressing in the high-pressure press with polished sapphire, glass and / or diamond disks and form factors adapted to the area of application may be preferred

Pressing tools done.

To avoid contamination of the tablet surface by the metallic die and to achieve a very smooth and even surface, a sapphire disk can be placed between the powder and the die.

In particular, the wet milling may be carried out with a liquid, wherein the liquid may be water, deionized water and / or an organic solvent. With regard to the milling protocols, the main parameters that change depending on the material, the amount of water and the grinding time, with other parameters such as

Revolution speed (acceleration), etc. can be additionally varied. As an example, the following milling protocols for geological / environmental materials are listed:

Ores, fly ash: 30 min, 10 ml D.I. water

Basalt (mafic rocks) 45 min, 5 ml D.I.

Carbonate / phosphate: 15 min, 10 ml D.I. water

Granite and similar: 60 min, 5 ml D.I.Water

Ultramafic rocks: 45 min, 5 ml D.I.Water

The pressed tablets / pellets made with one of the foregoing

Press tablets / pellet manufacturing processes of nanoparticulate pressed tablets / pellets of synthetic and / or natural materials are also worthy of protection.

Furthermore, the use of the preceding compressed tablets / pellets produced using one of the preceding pressed tablet / pellet production methods of nanoparticulate pressed tablets / pellets of synthetic and / or natural materials as particularly certified according to ISO guidelines, reference material for solid analysis method is particularly advantageous.

Further, the foregoing pressed tablets / pellets prepared by one of the foregoing press-tablet / pellet manufacturing methods of nanoparticulate pressed tablets / pellets of synthetic and / or natural materials may be used as direct medium

Solid analysis can be used.

The perspective of this development is that in the future no wet laboratory will be needed for the digestion of solids, as these types of wet laboratories are associated with considerable expense for purity and high risks due to hazardous substances.

Overall, the following advantages result:

in order to produce mechanically stable tablets from undiluted original powder no addition of binder is necessary because of the very high cohesion of the nanoparticles, which is why no dilution / material change of the original material takes place;

Due to the extremely small particle size of the nanoparticles <100 nm, there is a very low heterogeneity in analyzes with spatial resolution in the range of 1-100 μηι;

it is the ideal way to homogenize natural or synthetic materials; the mixture and homogenization of different solids is possible; the stability under high vacuum and under high-energy radiation (electron beam, ion beam) is given;

the surface is extremely flat and smooth (roughness <30-150 nm); Compacts are ultra-homogeneous, stable and have an extremely smooth and even surface;

- Extremely homogeneous solids, also manufactured according to ISO and REMCO guidelines, suitable as certified standard reference materials (SRM) for a variety of materials for element and isotopic composition;

addresses the worldwide extreme lack of homogeneous solids that can be used as micro-SRM;

- is suitable for many micro-analytical methods with X-ray, laser, electron and

ion beam, the huge problem of the worldwide lack of homogeneous SRM is solved by it;

self-contained analysis method for elemental analysis of solids on major to ultra trace element composition is possible, thereby eliminating wet laboratories with hazardous materials;

Waiver of addition of grinding or pressing aids;

homogeneous mixture of different materials as nanopowder without phase separation.

An embodiment of the invention will be described in detail below with reference to the accompanying drawings, wherein the description is intended to illustrate the invention and not to be considered as limiting. In addition, the prior art will be explained.

Show it:

Fig. 1 is a schematic representation of an embodiment of the known in the prior art manufacturing method and

Fig. 2 is a schematic representation of an embodiment of the disclosed here

Manufacturing process.

In Fig. 1 is a schematic representation of an embodiment of the known in the prior art manufacturing process is shown.

Here, first the starting material p is finely ground (<75 μm) and in the

For example, cellulose, wax, boric acid, organic compounds, etc. mixed A (b) and homogenized H. Subsequently, an aliquot thereof (p + b) _{H is added} in a high pressure hydraulic press of 5 to 20 liters of a tablet / pellet t (p + b) _H pressed P.

Fig. 2 shows a schematic representation of an embodiment of the manufacturing method disclosed herein. In a first step, 3-4 g of finely ground powder p of the original material are weighed in a grinding cup, for example made of agate, under a so-called clean bench in a particle-free atmosphere.

The grinding bowl already contains a certain amount of grinding balls made of agate, with diameter and total mass of the grinding balls according to the material (grinding protocol).

Grinding balls and cups had previously been cleaned by grinding of high purity (optical grade) quartz powder. There is still an addition of de-ionized water (DIW,> 18.2 MOhm), the amount depends on the material to be ground (grinding protocol) and is such that during the suspension, a suspension with oil-like viscosity is formed. Subsequently, a closure of the grinding bowl and insertion into a ball mill.

This is followed by a wet milling M in a high-energy ball mill in

Interval operation.

The grinding time is material-specific and has been optimized for a number of materials (milling protocol). This produces particles with particle sizes in the nanometer range (30-150 nm, Ο ₉₀ <1 μΓΤΐ).

The ready-milled nanopowder p _M is rinsed as a suspension with DIW from the balls and the grinding bowl and transferred with a pipette into a pre-cleaned plastic cup. The plastic cup with the suspension (about 50-100 ml) is flash frozen at -80 ° C and then dried in a freeze dryer G over 72-96 h.

The dried nanopowder PMG is transferred to a hand mortar made of agate and rehomogenizes H.

The rehomogenized nanopowder P _M GH is weighed into the die (approximately 600 mg for a 13 mm diameter tablet), which is then inserted into a programmable hydraulic tablet press, and the powder is then added at 10 t / cm 2 (for 13 mm diameter Press protocol) over 1 minute compressed P.

To avoid contamination of the tablet surface by the metallic pressing punch and to achieve a very smooth and even surface, a sapphire disc is placed between powder p _M G and ram. Depending on the analytical application

Tablets t (p _MG H) of various diameters (eg 5, 10, 13, 32 mm) were prepared. LIST OF REFERENCE NUMBERS

A addition of a binder b

B binder

G freeze-drying

H Rehomogenize

M grinding process / wet grinding

P crimping

P powder, finely ground

PM powder, ground

PMG nanopowder / powder, ground and freeze-dried

PMGH homogenized nanopowder / powder, ground, freeze-dried and rehomogenized p + b powder with binder

(p + b) _H powder with binder, homogenized

t pellet, tablet

Claims

Press tablets / pellet manufacturing processes of nanoparticulate pressed tablets / pellets of synthetic and / or natural materials comprising the steps of:

- Preparation of a fine analysis powder (p) with grain size <75 μηι

and

- pressing (P) at least one aliquot thereof in a high-pressure press into a tablet / pellet (t),

characterized in that

between the above steps:

- First, a wet milling (M) of the fine-finely ground powder (p) in a grinding arrangement, Jet Mill grinding arrangement and / or

High energy ball mill grinding arrangement to a regrind (p _M ) takes place;

- Subsequently, a transfer and drying, thermal drying or

Freeze-drying (G) of the ground material (p _M ) to a nanopowder (P _M G) takes place

and

- Then rehomogenize (R) of the dried nanopowder (PMGR) takes place, wherein

- The at least one aliquot for pressing of the dried and

rehomogenized nanopowder (PMGR) is selected,

- The pressing is done without the addition of a binder,

and

- A nanoparticulate powder P with grain sizes D ₉₀ <1 μηι is formed.

Press tablets / pellets production process of nanoparticulate pressed tablets / pellets according to claim 1,

characterized in that

the nanoparticulate powder P with grain sizes in the range of 30-150 nm with D ₉₀ <1 μηι is formed.

Press tablets / pellet production process of nanoparticulate pressed tablets / pellets according to claim 1 or 2,

characterized in that

Pressing (P) of the aliquot (PMGR) is carried out in a high-pressure press in the working range of 2 to 80 t, 3 to 40 t or 5 to 20 t. Press tablets / pellet production process of nanoparticulate pressed tablets / pellets according to claim 3,

characterized in that

Pressing (P) in the high-pressure press with polished sapphire, glass and / or

Diamond discs and form factors adapted to the application area

Pressing tools takes place.

Press tablets / pellets production process of nanoparticulate pressed tablets / pellets according to claim 1, 2, 3 or 4,

characterized in that

the wet milling (M) is carried out with a liquid, wherein the liquid is water and / or an organic solvent.

6. compressed tablets / pellets made with any of the foregoing compressed tablet / pellet manufacturing processes of nanoparticulate pressed tablets / pellets of synthetic and / or natural materials.

Use of the foregoing compressed tablets / pellets made with one of the preceding press tablet / pellet nanoparticle production processes

Pressed tablets / pellets of synthetic and / or natural materials as

Reference material for solid analysis method or as medium for the direct

Solid analysis.